Thio formal synthetic lubricants



United States Paten'tOi 2,858,274 Patented Oct. 28, 1958 free Serial No. 416,688 3 Claims. 01."252- 485 This invention relates to synthetic lubricating compositions; particularly theinvention relates tosynthetic lubricating compositions having outstanding lubricating properties at high and low temperatures'and which have the advantage of leaving substantially no combustion chamber deposits in the cylinders of reciprocating engines.

More particularly, the invention relates to newandimproved synthetic lubricating Y oils Q "which comprise "the formals of organic compoundsfhaving at least one free hydroxyl group which is alcoholic in" nature and which contains alinkage wherein n and z are small whole numbers, wherein x. and

w are a number from 'to. 8, wherein is 1to2. I

Especiallypreferred and contemplatedjn the preferred embodiment of this inventionai'e complek' 'thioflformals of the formula wherein A and B may be alike-or different and are selected from the group consisting-of organic radicals containing from 1 to 60 carbon atoms whichcorrespond to organic compounds containing a hydroxyl'group. that is alcoholic in nature, wherein n is a small whole number, wherein x is a number from 0 m8, wherein y is l to 2, and wherein z is a small whole number. A and B are preferably selected such that the total number of carbon atoms in the complex thio-formal is between about 20 and 13.0, compounds containing from about 25 to about 100 carbon atoms being especially preferred. The organic hydroxy compounds which serve as a source for the radicals A and B will be defined more in detail below.

For use in reciprocating engines, particularly as a lubricant for automotive engines, alubricating composition must meet several requirements. In order to form an effective lubricating film and to maintain that film at low and high temperatures itmust have certain viscosity characteristics. At low temperatures the lubricant must be sufficiently labile to flow through the circulatory system of the equipment and allow movement of lubricated surfaces without an undue power requirement. A lubricant having an ASTM pour point below about 353; l..; 1 1as sufficient low temperature lability to make it satisfactory in these respects for general use.

At high temperatures a lubricant must have sutlicient body or thickness to furnish and maintain a satisfactory lubricating filrn.

It has been found that a lubricant ,thatjs, satisfactory in this respect' will have a viscosity at 219 of b etween about 2 and 60 centistokes, i. e;, 32.8 and 280 Sayibolt seconds, Universal. To prevent undue lubricant loss, due to volatility and general molecular disintegration and to insure against explosion hazards at higher temperatures 2 sometimes encountered, a lubricating composition should have a flash point in excess of about 300 F. Dhese requisites are inherent in the term lubricating compositions, as used in this specification, and the thio formals of this invention are limited to those within these operable ranges. The preferred materials, as contemplated herein and as described in the preferred embodiment hereof, will have an ASTM pour point below about 15 F., a flash point above about375 F., and will have a viscosity within the range of 2.6 to 13 centistokes, i. e., 35 to 70 Saybolt seconds, Universal, at 210 F.

' In general, it has been found that the above listed properties are a function both of molecular structure and of molecular weight. This fact makes it possible, Within certain limits, to prepare compositions-having similar low and high temperature properties in a variety of ways and also enables the manufacturer to tailor a composition to fit a certain set of specifications withi'nvrather general limits. This fact alsoaccounts for the large number of organic materials containing=alcoholic hydroxyl groups available for preparing the compositions offthis invention.

In general the preparation of the thio formals of this invention is accomplished by methods that require conventional techniques and methods. Three general lines of approach may be followed.

('1) All of the reactants may be admixed in the reacting zone and heated to reflux temperature in the presence of an entraining agent such as.hexane, hepta'ne or the like. After recovery of the calculated amount of water in this one-step process, the product is washed free of any acidic catalysts and stripped free of unreacted components.

(2) A secondapproach is to admix x .moles of the thio glycol reactant with x1 mols of formaldehyde to obtain the central portion of the complexformal, i. e., the portion represented by In another reacting zoneequal-mols of an alcohol and formaldehyde are heated to about 60 C. to obtain the hemiformal of the alcohol, i. e., RO-CH --OH. The materials are then. blended by adding the thio glycol formal to the alcohol hemiforrnal and heated to reflux temperature. The product, after removalof the theoretical .amount of water, is then washed and stripped as above.

(3) In still a third approach, the hemiformal of the chosen alcohol is first made by heatingequal. mols of the .alcohol and formaldehyde. Then tothis is added the desired molar proportion of a thio glycol and formaldehyde and the total mixture heatedtor'eflux, temperature to make the hydroxy complex represent'edby Two mols of this material is then reacted with one mol of formaldehyde to obtain the product which is purified as above.

The materials used to prepare these formals,'.that is organic hydroxy compounds. containing at least one free 'hydroxyl group which is alcoholic in character, may'be e. n-Butyl alcohol f. Iso-butyl alcohol genated to a primary alcohol. This process is described 'in U. S. Patent No. 2,327,066 issued to Roelen in 1943.

g. Sec.-butyl alcohol 7 lgg g' i gg figi It has been found that particularly desirable alcohols j'. Iso-arh l alcohol v. for the formation of the thio formals of this invention f-- fifgg gfggfig v l can be prepared by the application of the 0x0 synthesis 11'. Z-ethyl-l-butanol to polymers and copolymers of C and C mono0lefins. 2' g g g fgf These monoolefins are readlly available in petroleum ISO-Lam alcohol refinery streams and processes for their conversion to g fggfgifiifigi I liquid copolymers have been worked out by the art. Qne s1 Decyl alcohol 1 such process, known as U. 0. P. polymerlzatlon, consists f; i gg i gg of passing the olefin-containing stream in hquld phase in v: Pentadecyl alcohol contact with an acid catalyst comprising phosphoric acid v Octadecyl impregnated on kies'elguhr. Other acidic catalysts, such AIM alcohol h h 'd r h h t m re nated on y.'Cr0tyl alcohol as p osp one am 01 coppe p osp ae 1 p g Oleyl 15 silica gel, sulfuric acid, Friedel-Crafts catalysts, actlvated all, The terpineols bb. C to C Oxo alcohols cc. Alcohols derived from the Synol" process dd. Alcohols derived from the oxidation of pa ,troleum fractions 'ee. Alcohols derived from Guerberts reaction 17'. Alcohols derived from the hydration of olefins gg. Alcohols derived from the Oxyl synthesis hh. Mixtures of the above it. The corresponding mercaptans 2. Aromatic:

clays, silica-alumina, copper pyrophosphate, etc., may be used. Suitable conditions when employing phosphoric acid catalysts Of: the U. 0. P. type are temperatures of 300? F. to 500? E, pressuresfrom 250 to 5,000 p. s 1. and feed stocks comprising refinery streams contalnlng propylene. and mixedbutylenes. Suitable feed stocks, for example, may contain from 15 to 60' mol percent m Benzyl alcohol propylenes,-fror n 0,5 to 15 mol percent butylenes and Phenylethyl alcohol a from 0.1 to 10 ,mol percent isobutylene, the remaining g'phenyll'pmpal-ml being saturated hydrocarbons. Other suitable feed stocks a-Naphthyl carblnol v Cinnamyl alcohol are the dimer andtrlmer of sobutylene. ,Diphenyl The preferred. Oxo alcoholsemployed in forming the Furfuryl alcohol r Y Cumic alcohfill thlo formals of thls invention are those having from 8 Vanill lalco o Pipemynyl alcohol to 20 carbon atoms derived from olefin copolymers hav I The corresponding melcaptalis mg from 7 to 19 carbon atoms. In preparlng these 0x0 g fi amhm alcohols the desired olefin fraction is segregated from onohydric r H V H o,

- 1 Aliphatic: the crude olefin polymer product by fractionation.

. o a. Halogefilfiiltegl a1c0h0 The following table for example, shows the structure one chlorohydrln v a f I and percent composltlon of C O xo alcohols prepared frorn a" C olefinstream which had been fractionated others of polyalkylene glycols "from i the products obtained by the phosphoric acid b'oEthanolamme polymerization of refinery gas streams contaimng c. 2-amin0 gropanol .d.-2-nitroet anol propylene and mixed nand lsobutylenes.

e L Y (1 Ethylene glycol monoacetate (2 Propylene glycol monobutyrate (3 Butylene glycol monolaurate (4 Polyethylene glycol monoesters es-s s s (3) Propylene chlorohydrin (4) The various chloro-substituted mono- 2-nitrobutanol The various glycol monoesters, e. g.

Strtlcture oi Ca 0x0 Alcohols Prepared from C -C4 Copolymer Heptanes Percent (1 (2 Tri uoro ethanol 2-nltropropano1 (5) Polypropylene glycol monoesters 6) Polybutylene glycol monoesters r i f 9 various glycol monoethers, e. g.- Ethylene glycol mono-methyl ether 2) Propylene glycol mono-butyl ether 3) Butylene glycol mono-lauryl ether 4) Polyethylene glycol mono-ethers. V 5) Polypropylene glycol mono-others 6; Polybutylene mono-others 7 Polytrimethylene glycol mono-others 5O Y I 1 The varlous glycol mono-formals, e. g. the c mixed formals of glycols and alcohols 1. Hydroxy alkyl cyanides 1) Ethylene cyanohydrin 2) a-Hydroxy-isobutyronitrile k. Ethanol morpholine 2. Aromatic:

a. p-Methoxy benzyl alcohol b. The various chlorobenzyl alcohols c. The various nltrohenzyl alcohols d. 2 anilino ethanol B. Other Hydroxy Compounds 1.- Esters of hydroxy acids:

a. The various lactate esters b. The var ous glycolate esters c. The various hydroxy stearate esters 2. Carbonyl substituted alcohols:

a. Hydroxy ketones, e. g.-(1) Hydroxy aceyroxyaeyes.e.g.-

( 1) r-Hydroxy adipaldehyde (2) B-Hydroxy propionaldehyde Particularly desirable organic hydroxy compounds for use in this invention are those highly 'branched'chain I -0 aliphatic alcohols prepared by the OX0 synthesis. This Oxo synthesis may be described as being the catalytic reaction of an olefin with carbon monoxide and hydrogen. The reaction occurs at temperatures in the order. of 300400 F., at pressures in the range of about 1000 to 3000 p. s. i., in the presence of a suitable catalyst, ordinarily a heavy metal carbonyl such as cobalt carbonyl. The resulting aldehyde is subsequently hydro- 0 wasi'statediabove, the thio 'formals of this invc tion may b'e' considered to have the following general formula from the group consisting. of organic radicals containing from :1 to 60 carbon atoms which correspond to organic compounds containing a hydroxyl group that is :alcoholic in nature, wherein n-is a'sma-ll whole number, wherein xis a number from 0 to 8,, wherein y is 1 to 2, and wherein z is a small whole number. The sum of the carbon atomsinthe molecule should be betweenf20 and 130 and .preferablybetween about 251-and 100.

The group of organic compounds that satisfy the .conditions-of the above generic formula and that are used to build some of the compounds according to the concept of this invention are m'onohydric alcohols, thiodiglycols and organic acids. These compoundsmay be advantageously combined withformaldehyde to form molecules having the following type formulas, words instead of structures being .given toshow the components of the complex .formals:

Alcohol (formaldehyde thio'diglycol z Thioglyco1-(formaldehyde-thiodiglycol) Polymethylene and polyalkylene glycol (formaldehydethiodi glycol z Thiogl yc-ol' monoester-i(formaldehyde-thiodiglycol) z Thiogly'col mon'oether- (formaldehyde-thiodiglycol) z In all formulas given above z represents a whole number. The acids which may be used to prepare the glycol monoesters may be selected from the following partial list:

According to a second concept of the instant invention, the molecules set out by the type formulas above that have a free hydroxyl' groupmay be further treated with formaldehyde and-joined to another organic compound having a'freealcoholic hydroxyl group. This series of compounds, all of which the grouping(formaldehydethiodiglycol) x being one or greater than 1, may be shown as follows; the common grouping being designated by Z:

Al-cohol Z-formaldehyde-alcohol Alcohol-Z-formaldehyde-glycol monoester Alcohol-Z-formaldehyde-glycol monoether Glycol monoester-Z-formaldehyde-glycol monoester Glycol monoester-Z-formaldehyde-glycol monoether Glycol nionoether-Z-formaldehyde-glycol monoether aaaaem 6 By substituting a hydroxy acid monoester such as lactates and glycolates, another series of compounds may be prepared as follows:

Hydroxy monoester-Z-formaldehyde-hydroxy monoester Hydroxymonoester-Z-formaldehyde-alcohol Hydroxy monoester-Z-formaldehyde-glycol monoether Hydroxy monoester-Z-formaldehyde-glycol monoester It will be seen that the above mentioned complex formals all are included under the generic formula:

wherein A andB may be alike or different andare selected from the group consisting of organic radicals containing from 1 to carbon atoms which correspondto organic compounds containing ahydroxyl group that is alcoholic in nature, wherein n is .a small whole number, wherein x is a number from 0 to 6, wherein y is 1 to 2, and'wherein z is a small whole number.

This concept of the instant invention may be illustrated as follows:

EXAMPLE v1.COMPLEX THIOFORMAL FROM C OXO ALCOHOL, FORMALDEHYDE AND THIO- DIGLYCOL J Preparation of 1.2 mols of complex thioform al A lcohol-CH O (thi0diglyc0l-CH O -alcohol C Oxo alcohol (480 g), obtained by oxonation and hydrogenation of tetrapropylene, was heated for 1 hour at 50C. in the presence of paraformaldehyde (108 g) heptane (300 g.) and NaHSO (2.2 g.) catalyst; 'The thiodiglycol (293 g.) was then added and the temperature raised to-refiux C. from which it gradually increased to 117 C. after 3 hours. 70 cc. of water was collected. The material'was decanted from the catalyst after cooling and washed with three cc. portions of saturated Na- CO solution and then three 100 cc. portions of water. The material was then filtered and stripped to a liquid temperature of 186 C. at 0.7 mm. pressure. The liquid thus obtained was clear, had a light straw color and contained 0.93 sulfur (theory=0.94%

EXAMPLE 2 TABLE I.PHYSIOAL PROPERTIES OF THIO-FORMAL SYNTHETIC LUBRL o 1 it? 1 $3 Com lex Complex 75% omp ex 10- p ex 10- l l ii gli Thio di- Thiodi- Complex plex Ester diglycol diglycol glycol glycol glycol Ester B Z B, 25% Formal Formal Formal, Formal, Ester A l Dlester 3 (Early) m (Exol), 1n EX I Ex. 11 Diester 3 Dlest er 3 o I itii fil jl 7. 1 5. 5 7.78 10. s 8.0 3. s 3. 5 40. 8 25. 7 40. 9 52. 3 39. 9 l4. 2 13. 6 2, 080 760 Orysta1s 1, 600 1, 000 235 221 45, 000 12, 400 Solid 25, 13, 000 2, 000 1, 820 136 156 148 152 155 158 15% --60 75 35 -60 65 75 --7o 425 405 460 480 435 425 425 Ale 8 Diester Di-2 ethyl hexyl sebacate.

1 Complex Thlodiglycol Ester A 0 0x0 Alcohol-Adipic AcidThiod iglycol-Adipic Acid-C Oxo h' l. I I o inplex Ester B 2Ethyl hexanolSebacie Acid-Polyethylene glycol-Sebacrd Ac1d2-Ethy1 hexane],

TABLE II.LOAD CARRYING ABILITIESOF COMPLEX SYNTHETIC LUBRICANTS BLENDS 'OF ABOVE COMPLEXES IN DI-Z-ETHYLHEXYL SEBACATE (D. O. S.)

D. O S 10% Complex Thiodlglycol Formal f 700 850 D. O. S. Complex Ester A 750 700 D. O. S. 10% Complex Ester 13.- 600 650 D. 0 S 450 550 It will be seen from an examaination of the data in Table I that the complex thiodiglycol formals of this invention compare very favorably with the complex esters of the prior art. It will also be noted that the low temperature viscosity of blends of the material of the inventive concept are much superior to the blends containing the known complex esters and possessing comparable load carrying ability. This improvement in the low temperature viscosity property is quite important as will be pointed out in more detail below.

It has been found that the complex tbioformals of this invention possess outstanding high load carrying ability superior to that of any of the complex esters hitherto known. The load carrying ability of the materials of this invention are compared with prior art complex esters in Table II. The load carrying test which may be designated as the SAE-SOD test is carried out in the conventional SAE Lubricant Tester employing a 3.421 gear ratio. After a run-in period of 2 minutes at a 50 lb. load, the load is increased manually by 50 lbs. every 10 seconds until scuffing occurs. The load at the scufiing point indicates .the load carrying ability of the lubricant being tested.

Two tests are generally sufiicient to characterize the lubricant as shown in Table II.

It will be seen that the load carrying ability of the complex thiodiglycol formals of this invention are outstandingly superior to those of the prior art. This becomes of exceeding importance in preparing blends of diesters for use in aircraft engines. Since the complex thiodiglycol formals of this invention have a much higher load carrying ceiling, lower concentrations can be used to get a high load carrying characteristic in the final blend without seriously increasing the blend viscosities. This is pointed out clearly in the data above. In Table II it is seen that blends of 10% of the complex thioformals of this invention in 90% di-Z-ethyl hexyl sebacate have load carrying abilities of from 700 to 850 lbs. From Table I it is seen that these blends have viscosities of less than 2000 centistokes at 40 F. (2000 cs. at 40 F. is considered equivalent to 13,000 cs. at 65 F., the maximum permissible for MILL-7808A approval). Both complex esters of the prior art were unsatisfactory at low temperatures and when blends were prepared having a comparable load carrying ability, these too were unsatisfactory because of cloudiness, crystallization or excessive viscosity.

The complex thioformals as described herein may serve as the lubricant base for grease compositions. These synthetic lubricants may be thickened to stable grease structures with conventional grease forming soaps such as lithium soaps of high molecular weight substantially saturated fatty acid, the n-acyl p-amino phenols, silica gels,

treated bentonites and the like. Oxidation inhibitors; rust inhibitors, tackiness agents and other grease addi-' tion agents may be added to the complex formal greases.- The soap complexes known to the art made by using low molecular weight acid salts may also be used in preparing these grease compositions. If desired the complex' formals of this invention may be blended with mineraloil or other synthetic lubricants such as simple bis-formals, complex esters, di-esters such as di-Z-ethyl hexyl sebacate, C Oxo adipate, and the like, pentaerythritol tetracaproate, phosphates, siloxanes, silicates, ph0sphonates and the like and a grease composition which incorporates the desirable characteristics of the blends may be preparedby conventional techniques.

To summarize briefly the instant invention relates to new compositions of matter which have outstanding utility as synthetic lubricating compositions. The materials contemplated may be broadly described as being thioformals of organic materials containing at least one hydroxyl group that is alcoholic in nature. By thioformal is meant materials containing at least a sulfur ether linkage not adjacent to the formaldehyde methylene groups and one or more formal linkages. The structure of the formals of invention may be described as one corresponding to the formula:

wherein A and B may be alike or different and areselected from the group consisting of organic radicals: containing from 1 to 60 carbon atoms Which correspond. to organic compounds containing a hydroxyl group that. is alcoholic in :nature, wherein n is a small whole number, whereinx is a number from 0 to 8, wherein y is l to 2 and wherein z is a small whole number.

The total number of carbon atoms in the molecule: should be between about 20 and 130, preferably between: about 25 and 100. The compounds that are especially preferred and that are considered to be the preferred embodiment of this invention are those materials which have a kinematic viscosity at 210 F. within the range of from 2 to 60 centistokes, an ASTM pour point of at least as low as 35 F., and a flash point of at least 300 F.

The thioformals of this invention are useful as lubricants, plasticizers, solubilizers, grease bases, insecticides, weed killers, rust preventives, solvents, dewaxing aids, detergents, and as raw materials for many other industrial applications, such as household detergents, fumigants, etc. These new synthetic lubricating oils may be admixed with other lubricating oils, naturally occurring or synthetic, either as concentrates oras finished blends. They are compatible and may be blended with the well known lubricant addition agents such as viscosity index improvers, pour point depressors, detergents, rust inhibitors, antioxidants and the like.

What is claimed is:

1. A synthetic lubricating composition comprising about of di-Z-ethyl hexyl sebacate containing combined therein about 10% of a complex thioformal of the formula 2. A synthetic lubricating composition comprising a major proportion of a synthetic carboxylic acid ester having lubricating characteristics and a minor amount sufficient to improve the load carrying ability of said lubricating oil of a complex thioformal having the formula 3. A synthetic lubricating composition according to claim 2 wherein said carboxylic acid ester is an ester of a dicarboxylic acid.

References Cited in the file of this patent UNITED STATES PATENTS Subkow June 7, 1949 

1.A SYNTHETIC LUBRICATING COMPOSITION COMPRISING ABOUT 90% OF DI-2-ETHYL HEXYL SEBACATE CONTAINING COMBINED THEREIN ABOUT 10% OF A COMPLEX THIOFORMAL OF THE FORMULA 